YouTube:W8BYA -
A demonstration of SWR measurement differences using four different instruments on a 2 meter antenna.
In particular is the use of the new Siglent reflection bridge for the SSA 3021X spectrum analyzer.
Approximate cost of each instrument:
Bird 43 -- $600
AIM4300 (new version of the AIM4170C) -- $495
Siglent 3021X -- $1600
Agilent 8712ES -- $2600

Antenna Modeling (by AC6LA) - An excellent resource on antenna modeling software.
Be sure to checkout the program called Transmission Line Details.
Good information on the variation of transmission line parameters versus frequency.
Also check this new program that works in conjunction with EZNEC for evaluating antenna and transmission line systems: AutoEZ